Emergence of Vibrio cholerae Serotype Hikojima in Northern Tamil Nadu.

Sir,

In 2009, a total of 155 stool samples were collected from patients suffering from cholera like illness. 13 isolates of Vibrio cholerae were obtained. They were identified, biotyped and serotyped by standard procedures.

All the 13 Vibrio cholerae O1 isolates were of El Tor biotype, and serotype Hikojima. No other serotypes were found in this study. The serotype Hikojima is known to be very unstable, and has been demonstrated to interconvert and undergo serotype switching.(1) So the study reflects the importance of close monitoring and surveillance of the prevalent serotype.

Out of the 13 isolates first case was reported in Feb 2009. Maximum of 4 cases were reported in August 2009. Among the 13 isolates most of the patients were from Vellore and the rest from neighbouring towns. Males (61.53%) were more affected than females (38.45%). All the cholera cases were in the pediatric age group (1 to 10 years). More cases were seen in the age group less than 2 years (38.46%). This was similar to previous studies from other parts of the country which showed that the infection rate of cholera is increasingly reported in children.(2)

The antibiogram [Table 1] of 13 isolates showed 100% resistance to cotrimoxazole and nalidixic acid. However the sensitivity to ampicillin was variable, 46% isolates were highly sensitive, 31% showed moderate sensitivity and 23% showed resistance to ampicillin. This correlated with earlier studies(34) that reported resistance of Vibrio cholerae isolates to ampicillin, cotrimoxazole and nalidixic acid.

Table 1

Sensitivity pattern of Vibrio cholerae isolates n=13

Although ciprofloxacin resistance has been reported in India(34) in case of Vibrio cholerae O1 El Tor Ogawa, Hikojima strains isolated at our place were found to be 100% sensitive to ciprofloxacin in accordance with study by Neelam Taneja et al.(5) All the 13 isolates were sensitive (100%) to azithromycin.

Previously ciprofloxacin, doxycyclin and tetracyclin were used as first line drugs in treatment of cholera. These drugs are not used in children due to their side effects. In present study only children were affected so azithromycin which showed 100% sensitivity could be used effectively and safely as the drug of choice in children to treat cholera.(67)